The studies were conducted at the Agricultural Experimental Station of the Institute of Soil Science and Plant Cultivation – National Research Institute in Grabow, during the years 2004-2006. The experiment was established by the split-plot– plit-block method at 4 replications on a soil of the very good rye complex, class IIIa. The first order factor were blue lupine varieties: thermoneutral – Sonet and Graf, and non-thermoneutral – Wersal and Boruta. The second order factor were sowing dates: I – very early (beginning of April), II – two weeks after the first date, and III – four weeks after the first date. The aim of the study was the estimation of dynamics of plant growth, development and yielding of thermo- and non-thermoneutral blue lupine varieties in dependence on sowing date. Distinct differences were found in the response of studied varieties to sowing date and weather course in the research years. Delay of sowing date caused greater increase of vegetative organs of blue lupine and considerable decrease of generative organs mass. It concerned most of the non-thermoneutral lupine varieties, since thermoneutral varieties changed the rate of mass accumulation only in a small degree. In the years which were characterized with average, for our country, weather conditions in the spring time, delay of sowing date caused a big decrease of non-thermoneutral varieties seed yield and considerably lower – of the thermoneutral ones. Considerable decrease of temperature in April or at the beginning of May caused vernalization of seedlings which were grown from seeds sowed also at later dates, therefore the response of both types of varieties to the sowing date was similar.